fix: Make default optional with a disabled config default

Author: jsonbailey

packages/sdk/server-ai/src/ldai/client.py

@@ -72,27 +72,30 @@ def completion_config(
         self,
         key: str,
         context: Context,
-        default_value: AICompletionConfigDefault,
+        default_value: Optional[AICompletionConfigDefault] = None,
         variables: Optional[Dict[str, Any]] = None,
     ) -> AICompletionConfig:
         """
         Get the value of a completion configuration.
 
         :param key: The key of the completion configuration.
         :param context: The context to evaluate the completion configuration in.
-        :param default_value: The default value of the completion configuration.
+        :param default_value: The default value of the completion configuration. When not provided,
+            a disabled config is used as the fallback.
         :param variables: Additional variables for the completion configuration.
         :return: The completion configuration with a tracker used for gathering metrics.
         """
         self._client.track(_TRACK_USAGE_COMPLETION_CONFIG, context, key, 1)
 
-        return self._completion_config(key, context, default_value, variables)
+        return self._completion_config(
+            key, context, default_value or AICompletionConfigDefault.disabled(), variables
+        )
 
     def config(
         self,
         key: str,
         context: Context,
-        default_value: AICompletionConfigDefault,
+        default_value: Optional[AICompletionConfigDefault] = None,
         variables: Optional[Dict[str, Any]] = None,
     ) -> AICompletionConfig:
         """
@@ -152,27 +155,30 @@ def judge_config(
         self,
         key: str,
         context: Context,
-        default_value: AIJudgeConfigDefault,
+        default_value: Optional[AIJudgeConfigDefault] = None,
         variables: Optional[Dict[str, Any]] = None,
     ) -> AIJudgeConfig:
         """
         Get the value of a judge configuration.
 
         :param key: The key of the judge configuration.
         :param context: The context to evaluate the judge configuration in.
-        :param default_value: The default value of the judge configuration.
+        :param default_value: The default value of the judge configuration. When not provided,
+            a disabled config is used as the fallback.
         :param variables: Additional variables for the judge configuration.
         :return: The judge configuration with a tracker used for gathering metrics.
         """
         self._client.track(_TRACK_USAGE_JUDGE_CONFIG, context, key, 1)
 
-        return self._judge_config(key, context, default_value, variables)
+        return self._judge_config(
+            key, context, default_value or AIJudgeConfigDefault.disabled(), variables
+        )
 
     async def create_judge(
         self,
         key: str,
         context: Context,
-        default_value: AIJudgeConfigDefault,
+        default_value: Optional[AIJudgeConfigDefault] = None,
         variables: Optional[Dict[str, Any]] = None,
         default_ai_provider: Optional[str] = None,
     ) -> Optional[Judge]:
@@ -222,7 +228,9 @@ async def create_judge(
             extended_variables['message_history'] = '{{message_history}}'
             extended_variables['response_to_evaluate'] = '{{response_to_evaluate}}'
 
-            judge_config = self._judge_config(key, context, default_value, extended_variables)
+            judge_config = self._judge_config(
+                key, context, default_value or AIJudgeConfigDefault.disabled(), extended_variables
+            )
 
             if not judge_config.enabled or not judge_config.tracker:
                 return None
@@ -346,7 +354,7 @@ def agent_config(
         self,
         key: str,
         context: Context,
-        default_value: AIAgentConfigDefault,
+        default_value: Optional[AIAgentConfigDefault] = None,
         variables: Optional[Dict[str, Any]] = None,
     ) -> AIAgentConfig:
         """
@@ -374,7 +382,8 @@ def agent_config(
 
         :param key: The agent configuration key.
         :param context: The context to evaluate the agent configuration in.
-        :param default_value: Default agent values.
+        :param default_value: Default agent values. When not provided, a disabled config is used
+            as the fallback.
         :param variables: Variables for interpolation.
         :return: Configured AIAgentConfig instance.
         """
@@ -385,7 +394,9 @@ def agent_config(
             1
         )
 
-        return self.__evaluate_agent(key, context, default_value, variables)
+        return self.__evaluate_agent(
+            key, context, default_value or AIAgentConfigDefault.disabled(), variables
+        )
 
     def agent(
         self,
@@ -457,7 +468,7 @@ def agent_configs(
             agent = self.__evaluate_agent(
                 config.key,
                 context,
-                config.default_value,
+                config.default_value or AIAgentConfigDefault.disabled(),
                 config.variables
             )
             result[config.key] = agent

packages/sdk/server-ai/src/ldai/models.py

@@ -152,6 +152,14 @@ class AIConfigDefault:
     model: Optional[ModelConfig] = None
     provider: Optional[ProviderConfig] = None
 
+    @classmethod
+    def disabled(cls):
+        """
+        Returns a new disabled config default with enabled set to false.
+        When called on a subclass, returns an instance of that subclass.
+        """
+        return cls(enabled=False)
+
     def _base_to_dict(self) -> Dict[str, Any]:
         """
         Render the base config fields as a dictionary object.
@@ -334,7 +342,7 @@ class AIAgentConfigRequest:
     Combines agent key with its specific default configuration and variables.
     """
     key: str
-    default_value: AIAgentConfigDefault
+    default_value: Optional[AIAgentConfigDefault] = None
     variables: Optional[Dict[str, Any]] = None
 
 

packages/sdk/server-ai/tests/test_agents.py

@@ -340,3 +340,26 @@ def test_agent_config_dataclass():
 
     assert config_no_vars.key == 'test-agent-2'
     assert config_no_vars.variables is None
+
+
+def test_agent_config_without_default_uses_disabled(ldai_client: LDAIClient):
+    """Test that agent_config uses disabled config when no default is provided."""
+    context = Context.create('user-key')
+
+    agent = ldai_client.agent_config('missing-agent', context)
+
+    assert agent.enabled is False
+
+
+def test_agents_request_without_default_uses_disabled(ldai_client: LDAIClient):
+    """Test that agent_configs uses disabled config when request has no default_value."""
+    context = Context.create('user-key')
+
+    agent_requests = [
+        LDAIAgentConfig(key='missing-agent'),
+    ]
+
+    agents = ldai_client.agents(agent_requests, context)
+
+    assert 'missing-agent' in agents
+    assert agents['missing-agent'].enabled is False

packages/sdk/server-ai/tests/test_judge.py

@@ -574,6 +574,23 @@ def test_judge_config_prefers_evaluation_metric_key_over_keys(
         assert config is not None
         assert config.evaluation_metric_key == '$ld:ai:judge:preferred'
 
+    def test_judge_config_without_default_uses_disabled(
+        self, context: Context
+    ):
+        """judge_config should use a disabled config when no default is provided."""
+        from ldai import LDAIClient
+        from ldclient import Config, LDClient
+        from ldclient.integrations.test_data import TestData
+
+        td = TestData.data_source()
+        test_client = LDClient(Config('sdk-key', update_processor_class=td, send_events=False))
+        ldai_client = LDAIClient(test_client)
+
+        config = ldai_client.judge_config('missing-judge', context)
+
+        assert config is not None
+        assert config.enabled is False
+
     def test_judge_config_uses_same_variation_for_consistency(
         self, context: Context
     ):

packages/sdk/server-ai/tests/test_model_config.py

@@ -3,7 +3,8 @@
 from ldclient.integrations.test_data import TestData
 
 from ldai import LDAIClient, LDMessage, ModelConfig
-from ldai.models import AICompletionConfigDefault
+from ldai.models import (AIAgentConfigDefault, AICompletionConfigDefault,
+                         AIConfigDefault, AIJudgeConfigDefault)
 
 
 @pytest.fixture
@@ -351,3 +352,63 @@ def test_sdk_info_tracked_on_init():
         },
         1,
     )
+
+
+# ============================================================================
+# disabled() classmethod tests
+# ============================================================================
+
+def test_ai_config_default_disabled_returns_disabled_instance():
+    result = AIConfigDefault.disabled()
+    assert isinstance(result, AIConfigDefault)
+    assert result.enabled is False
+
+
+def test_completion_config_default_disabled_returns_correct_type():
+    result = AICompletionConfigDefault.disabled()
+    assert isinstance(result, AICompletionConfigDefault)
+    assert result.enabled is False
+    assert result.messages is None
+    assert result.model is None
+
+
+def test_agent_config_default_disabled_returns_correct_type():
+    result = AIAgentConfigDefault.disabled()
+    assert isinstance(result, AIAgentConfigDefault)
+    assert result.enabled is False
+    assert result.instructions is None
+    assert result.model is None
+
+
+def test_judge_config_default_disabled_returns_correct_type():
+    result = AIJudgeConfigDefault.disabled()
+    assert isinstance(result, AIJudgeConfigDefault)
+    assert result.enabled is False
+    assert result.messages is None
+    assert result.evaluation_metric_key is None
+
+
+def test_disabled_returns_new_instance_each_call():
+    first = AICompletionConfigDefault.disabled()
+    second = AICompletionConfigDefault.disabled()
+    assert first is not second
+
+
+# ============================================================================
+# Optional default value tests
+# ============================================================================
+
+def test_completion_config_without_default_uses_disabled(ldai_client: LDAIClient):
+    context = Context.create('user-key')
+
+    config = ldai_client.completion_config('missing-flag', context)
+
+    assert config.enabled is False
+
+
+def test_config_method_without_default_uses_disabled(ldai_client: LDAIClient):
+    context = Context.create('user-key')
+
+    config = ldai_client.config('missing-flag', context)
+
+    assert config.enabled is False